In this type of process (DE-AS 16 52 990), the corrugation head bearing, which is located in a housing, permits a very limited axial displacement of the corrugation head. This displacement is not always sufficient to prevent sink marks in the tube wall, especially in the area of the weld seam, and as a result of irregularities in the metal structure of the band (hardness fluctuations). Furthermore, displacing the entire corrugation head requires extensive force, which leaves small markings in the tube material prior to the displacement, especially in thin-walled or weak band material. In extreme cases, differences in the hardness of the tube material can lead to deviations of the actual from the specified wave rise, or to tube collapse because the roller ring cannot keep up with the traction speed of the tube, or to a fracture of the roller ring, as a result of overload.
The corrugation head drive provided for a process of this type, with a coupling to the main drive motor through an infinitely variable gear, and the drive of the traction installation by the main motor, cannot fully eliminate the described defects, even with the selected limited axial displacement of the corrugation head.
It was proposed in a different type of process (DE-AS 20 49 235), in which the corrugation of the tube wall is produced by a corrugation tool that is screwed onto the smooth tube (screw corrugation process), that only the corrugation tool, i.e. the screw corrugator, be axially displaceable.
Transferring this proposal to a device with a corrugation roller failed, because of nearly unsurmountable difficulties.
The corrugation dimensions must be precisely maintained, particularly when such corrugated tubes are used as elements for the transmission of high frequency energy or signals. Sink marks in the corrugation lead to disturbing reflections of the transmitted waves, particularly at frequencies above 50 Mhz. This is even worse when the irregularities are evenly spaced.